1. Field of the Invention
The present invention relates to a method of manufacturing an organic light emitting display device and the organic light emitting display device. More particularly, the present invention relates to a method of manufacturing an organic light emitting display device and the organic light emitting display device, by which generation of dark spots by particles of a reflection film can be reduced.
2. Description of the Related Technology
Active matrix (AM) organic light emitting display devices (OLED) include an array of pixels. Each pixel includes a pixel circuit for driving an organic light emitting diode therein. The pixel circuit is electrically connected to a scan line, a data line, and a power supply line, and includes a thin film transistor (TFT) and a storage capacitor. The organic light emitting diode includes an anode, a cathode, and an organic light emitting layer interposed therebetween. The anode is typically formed of ITO film. The OLED further includes an encapsulating plate which covers the array of pixels.
Top-emission AM organic light emitting display devices typically display an image through the encapsulating plate. In the top-emission devices, the anode may further include a reflection film interposed between two ITO layers. However, since the reflection film is typically formed of an easily oxidizable metal, such as, Al, Mg, or Ag, an oxidized film is easily formed between the reflection film and the ITO film during formation of a hole to contact a driving thin film transistor (TFT) and the ITO film. The oxidized film increases the resistance of the ITO film and degrades the contact of the ITO film with the driving TFT.
In addition, the reflection film generates many particles while being manufactured, thus causing an electrical short between the anode and the cathode of the organic light emitting diode.
FIG. 1 is a photograph of a portion of an organic light emitting display device in which an electrical short occurred. In FIG. 1, a white layer which is the second from the bottom is an anode structure formed of ITO/Ag/ITO. A black layer immediately on the white layer is an organic emission layer (EL). A white thin layer right on the black layer is a semi-transparent cathode. As shown in FIG. 1, particles exist on the ITO/Ag/ITO anode structure, shorting the anode structure and the cathode. According to an element analysis, the particles are Ag. In other words, the particles are produced during formation of the reflection film.
The short due to the particles produces a dark spot on the displayed image. Accordingly, pixels including the dark spots become inferior. The number of dark spots produced by particles of a reflection film is at least 100 times greater than that of dark spots produced by particles of the ITO layer.